Immunosuppressive and complement-fixing effects of MAb DB81.
A. Inhibition of PBMC proliferation by MAb DB81. PBMC from 4 healthy blood donors were incubated with the indicated stimuli in a 5-day proliferation assay. Either no inhibitors (“nil”) or the indicated mAbs (3 µg/ml) were added at the beginning of the culture time. Proliferation was measured by incorporation of tritiated thymidine in triplicate wells. The values indicate the mean ± standard error of the mean. B. Complement fixation by MAb DB81. Flow cytometry analysis of PM-1 cells treated with complement only (C, top left) or with C plus thymoglobulin (polyclonal rabbit antibodies to human thymocyte antigens, ATG, bottom right), C plus MAb Leu-3a (bottom left) or C plus DB81 (top right). Cells were stained with propidium iodide as a marker for cell death. Numbers in panels indicate the percent of stained (complement lysed, dead) cells, which fell within the double arrow markers in the different experimental settings.